Transmission beam control method, adaptive antenna transmitter/receiver apparatus and radio base station

ABSTRACT

Changes in instructions for increasing/decreasing transmission power that have been decoded from TPC bits are monitored, and when the increase/decrease instructions in a prescribed time interval are biased toward instructions for increasing the transmission power, the peak direction or main lobe width of the transmission beam is changed by regulating the transmission power or transmission antenna weights that correspond to each of a plurality of antenna devices. These processes are repeated until the bias toward instructions for increasing the transmission power in the instructions for increasing/decreasing transmission power is eliminated or until the number of changes of the transmission beam reaches a maximum value that has been set in advance.

TECHNICAL FIELD

The present invention relates to transceiving device that is suitablefor use in a Code Division Multiple Access (hereinbelow abbreviated asCDMA) mobile communication system.

BACKGROUND ART

In a CDMA mobile communication system, a plurality of mobile stationstypically use the same frequency band to perform radio communication,and wave interference caused by the radio communication by other mobilestations, i.e., multi-user interference, is a chief cause of limitationof the subscriber capacity of a mobile communication system. To increasethe subscriber capacity, the adaptive antenna technology is effectivefor suppressing interference waves during reception, and duringtransmission, for avoiding transmission in unnecessary directions andthus reducing interference power that is applied to other mobilestations.

As a prior-art example of a transceiving device that adopts the adaptiveantenna technology (hereinbelow referred to as an adaptive antennatransceiving device), a technology that uses a plurality of antennadevices for controlling directivity is described in non-patent document1 (NTT DoCoMo Technical Journal, Vol. 8, No. 1, April 2000). Non-patentdocument 1 discloses increasing antenna gain in the direction of amobile station by conferring weight coefficients (reception antennaweights) to each of received signals that are received by a plurality ofantenna devices during reception, and during transmission, directing thetransmission beam toward the mobile station that is the object oftransmission by multiplying weight coefficients (transmission antennaweights) that are generated based on the reception antenna weights bythe transmission data for each antenna device.

As a method of generating the reception antenna weights, a method isdescribed in non-patent document 2 (S. Tanaka, M. Sawahashi, and F.Adachi, “Pilot symbol-assisted decision directed coherent adaptive arraydiversity for DS-CDMA mobile radio reverse link,” IEICE Trans.Fundamentals, Vol. E80-A, pp. 2445-2454, December 1997) for implementingcontrol so as to minimize the mean-squared-error between a pilot symbolafter despreading and a signal after RAKE synthesis that is generated byreferring to information data symbols that have been provisionallydetermined. In addition, non-patent document 3 (Tanaka, Harada, Ihara,Sawahashi, Adachi, “Outdoor test characteristics of adaptive antennaarray diversity reception in W-CDMA,” Shingaku Gihou, RCS99-127, pp.45-50, October 1999) describes an example of using the transmissionantenna weights that are generated based on the above-describedreception antenna weights in downlink transmission (transmission in thedirection from the radio base station to a mobile station).

In a CDMA mobile communication system, transmission power control(hereinbelow abbreviated as TCP) is generally implemented to ensuretransmission quality while avoiding unnecessary interference to othermobile station. In particular, the TCP technology is indispensable inCDMA because common frequency interference is produced by the assignmentof a common frequency to a plurality of mobile stations.

The relation between TPC and a transmission beam in downlinktransmission is next considered as an example.

In downlink transmission, the directivity of the transmission beam iscontrolled by using a plurality of antenna devices that are provided ina radio base station and multiplying the transmission antenna weights ofeach by transmission data. A mobile station instructs the radio basestation to reduce the transmission power if the reception qualityexceeds a desired value and instructs the radio base station to increasethe transmission power if the reception quality falls below the desiredvalue. The instructions to increase or decrease the transmission power(hereinbelow referred to as increase/decrease instructions) from themobile station to the radio base station use TPC bits that are includedin frames that are transmitted from the mobile station to the radio basestation in each of prescribed cycles. The radio base station extractsthe TPC bits from the frames that are transmitted from the mobilestations and increases or decreases the transmission power to thatmobile station in accordance with the instructions.

The following explanation regards an adaptive antenna transceivingdevice of the prior art with reference to FIG. 1. The adaptive antennatransceiving device that is shown in FIG. 1 is an example of theconfiguration for executing TPC in the adaptive antenna transceivingdevice that is described in FIG. 1 of non-patent document 1.

As shown in FIG. 1, this adaptive antenna transceiving device of theprior art is a configuration that includes: a plurality (N, where N is apositive integer) of antenna devices 301_1-301_N that are arranged in anarray; receiving-side multipliers 302_1-302_N for multiplying receptionantenna weights by the received signals that have been received byantenna devices 301_1-301_N; adder 303 for adding (synthesizing) theplurality of received signals that have been multiplied by the receptionantenna weights and supplying the result as reproduction data; receptionantenna weight generation circuit 304 for, based on the reproductiondata that have been supplied as output from adder 303, calculating theoptimum reception antenna weights that are to be multiplied by thereceived signals that have been received by each of antenna devices301_1-301_N and supplying the results to each of correspondingreceiving-side multipliers 302_1-302_N; TPC bit decoding circuit 307 forextracting TPC bits from the reproduction data and then decoding theseTPC bits to supply instructions to increase or decrease transmissionpower; antenna weight conversion circuit 305 for, based on the receptionantenna weights that have been generated by reception antenna weightgeneration circuit 304, generating transmission antenna weights, andfurther, increasing or decreasing the transmission antenna weight inaccordance with the instructions to increase or decrease transmissionpower that have been supplied as output from TPC bit decoding circuit307; and transmission-side multipliers 306_1-306_N for multiplyingtransmission antenna weights that have been supplied as output fromantenna weight conversion circuit 305 by transmission data and supplyingthe products to antenna devices 301_1-301_N. The adaptive antennatransceiving device that is shown in FIG. 1 shows the configuration of abaseband signal processor that performs signal processing of principallybaseband transmission/reception data. The adaptive antenna transceivingdevice includes a radio signal transceiver (not shown) that is providedwith an RF receiver for converting radio frequency signals that arereceived by antenna devices to baseband signals and an RF transmitterfor converting baseband signals to radio frequency signals.

In this configuration, antenna weight conversion circuit 305, based onthe weight coefficients (reception antenna weights) that have beengenerated at reception antenna weight generation circuit 304, generatestransmission antenna weights for transmitting in the same direction asthe directivity when receiving. In addition, antenna weight conversioncircuit 305 controls the transmission power by regulating eachtransmission antenna weight in accordance with the instructions toincrease or decrease transmission power that have been decoded at TPCbit decoding circuit 307.

Generally, reasons that can be considered for increasing thetransmission power of the radio base station include cases in which thereception quality of the mobile station deteriorates due to shieldingwhen the radio base station and mobile station are blocked by, forexample, buildings, or cases in which the transmission power isincreased to compensate for a drop in the reception quality of themobile station that is the object of transmission (hereinbelow referredto as the “desired wave mobile station”) because the peak direction ofthe transmission beam that is formed at the radio base station divergesfrom the desired wave mobile station.

When the peak direction of the transmission beam diverges from thedesired wave mobile station, the reception quality of the desired wavemobile station achieves the desired value through the TPC process, butwhen another mobile station is present in the peak direction of thetransmission beam, unnecessary interference power is applied to thismobile station, and the transmission power must therefore be increasedto each mobile station. The maximum transmission power of a radio basestation is normally limited by the capability of the power amplifierthat supplies power to the antenna devices, and an increase in thetransmission power to each mobile station therefore reduces thesubscriber capacity that can be accommodated by the mobile communicationsystem.

It is an object of the present invention to provide an adaptive antennatransceiving device that can reduce unnecessary interference power thatis applied to other mobile stations due to divergence of the peakdirection of a transmission beam from the mobile station that is theobject of transmission when applying TPC in downlink transmission, andthus, that can prevent the reduction of the subscriber capacity of amobile communication system.

DISCLOSURE OF THE INVENTION

In the present invention for achieving the above-described object,changes in instructions to increase or decrease transmission power thatare decoded from TPC bits are monitored, and when increase/decreaseinstructions are biased toward instructions for increasing thetransmission power in a prescribed interval that has been determined inadvance, the transmission antenna weights or the transmission power ofeach antenna device are adjusted to change the peak direction or themain lobe width of the transmission beam. These processes are repeateduntil the bias in increase/decrease instructions toward instructions forincreasing the transmission power is eliminated, or until the number ofchanges of the transmission beam reaches a predetermined maximum value.

When the peak direction of the transmission beam has been changed, thepeak direction of the transmission beam can be corrected toward thedirection of the mobile station that is the object of transmission.Alternatively, when the width of the main lobe of the transmission beamis increased, the reception power of the mobile station is increaseddespite slight deviation of the peak direction of the transmission beamfrom the mobile station that is the object of transmission.

The consequent reduction of increases in transmission power that arecaused when the peak direction of the transmission beam diverges fromthe mobile station that is the object of transmission enables areduction of the interference power that is applied to other mobilestations that are present in the peak direction and can prevent a dropin the subscriber capacity of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of an adaptiveantenna transceiving device of the prior art;

FIG. 2 is a block diagram showing the configuration of the firstembodiment of the adaptive antenna transceiving device of the presentinvention;

FIG. 3A is a schematic view showing the change in transmission powerduring application of TPC when the peak direction of a transmission beamis directed toward a mobile station;

FIG. 3B is a schematic view showing the change in transmission powerduring application of TPC when the peak direction of a transmission beamdiverges from the mobile station;

FIG. 4 is a schematic view showing the transmission beam control methodof the adaptive antenna transceiving device of the first embodiment;

FIG. 5 is a flow chart showing the procedures of the transmission beamcontrol method that is shown in FIG. 4;

FIG. 6 is a schematic view showing the transmission beam control methodof the adaptive antenna transceiving device of the second embodiment;

FIG. 7 is a flow chart showing the procedures of the transmission beamcontrol method that is shown in FIG. 6;

FIG. 8 is a flow chart showing the procedures of the transmission beamcontrol method of the third embodiment;

FIG. 9 is a block diagram showing the configuration of the adaptiveantenna transceiving device of the fourth embodiment; and

FIG. 10 is a block diagram showing an example of the configuration of aradio base station that is equipped with the adaptive antennatransceiving device of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following explanation regards the present invention with referenceto the accompanying figures.

First Embodiment

As shown in FIG. 2, the transceiving device of the first embodimentincludes: a plurality (N, where N is a positive integer) of antennadevices 101_1-101_N that are arranged in an array; receiving-sidemultipliers 102_1-102_N for multiplying reception antenna weights byreceived signals that have been received by antenna devices 101_1-101_N;adder 103 for adding (synthesizing) the plurality of received signalsthat have been multiplied by reception antenna weights and supplying theresults as reproduction data; reception antenna weight generationcircuit 104 for, based on the reproduction data that have been suppliedas output from adder 103, calculating optimum reception antenna weightsthat are to be multiplied with received signals that have been received,and for supplying these optimum reception antenna weights tocorresponding receiving-side multipliers 102_1-102_N; TPC bit decodingcircuit 107 for extracting TPC bits from reproduction data and decodinginstructions for increasing or decreasing transmission power; TPC bitmonitor circuit 108 for monitoring changes of the instructions forincreasing or decreasing transmission power that have been decoded byTPC bit decoding circuit 107 in prescribed intervals and detectingwhether or not a bias exists for instructions for increasing thetransmission power; antenna weight conversion circuit 105 for, based onthe reception antenna weights that have been generated by receptionantenna weight generation circuit 104, generating first transmissionantenna weights; transmission antenna weight control circuit 109 forcontrolling first transmission antenna weights based on the monitoringresults of TPC bit monitor circuit 108 and supplying the results assecond transmission antenna weights; and transmission-side multipliers106_1-106_N for multiplying second transmission antenna weights thathave been supplied as output from transmission antenna weight controlcircuit 109 with transmission data and supplying the products to antennadevices 101_1-101_N.

As with the prior art, the adaptive antenna transceiving device that isshown in FIG. 2 shows the configuration of a baseband signal processorfor realizing signal processing of mainly baseband transceiving data.The adaptive antenna transceiving device includes radio signaltransceiver (not shown) that is provided with an RF receiver forconverting radio frequency signals that have been received by antennadevices 101_1-101_N to baseband signals and an RF transmitter forconverting baseband signals to radio frequency signals. The basebandsignal processor may be constituted by a semiconductor integrated devicethat realizes the functions of each of the above-described constituentelements by, for example, logic circuits, or may be constituted by a DSPor CPU. When the baseband signal processor is constituted by a DSP orCPU, the processing described below of each of the constituent elementswith the exception of the antenna devices is executed in accordance witha program stored in advance in a storage device.

Reception antenna weight generation circuit 104 executes, for example,an MMSE (Minimum Mean Squared Error) process that updates receptionantenna weights such that the mean squared error between reproductiondata that have been supplied as output from receiving-side adder 103 anda predetermined reference signal (desired signal waveform) is minimized.Algorithms such as the LMS (Least Mean Square) algorithm or RLS(Recursive Least Square) algorithm are known algorithms for realizing anMMSE process, and no particular limitation is placed on the algorithmthat is used in reception antenna weight generation circuit 104 in thepresent embodiment.

Reception antenna weights W=(w₁, w₂, . . . , w_(N)) that are generatedin reception antenna weight generation circuit 104 are supplied to eachof receiving-side multipliers 102_1-102_N and antenna weight conversioncircuit 105.

Antenna weight conversion circuit 105 generates transmission antennaweights (first transmission antenna weights) W′=w′₁, w′₂, . . . ,w′_(N)) based on the reception antenna weights W=(w₁, w₂, . . . , w_(N))that are generated in reception antenna weight generation circuit 104.Antenna weight conversion circuit 105 is a device that is provided incorrespondence with each antenna device for executing a process forcorrecting the amplitude/phase deviation between a plurality of radiosignal transceivers that are not shown in FIG. 2, or a process forcorrecting the difference between frequencies when the frequencies ofthe transmission waves and reception waves are different as in thewell-known FDD (Frequency Division Duplex) system. Antenna weightconversion circuit 105 generates first transmission antenna weightsW′=(w′₁, w′₂, . . . , w′_(N)) for forming a transmission beam having adirectivity that is basically the same as the directivity duringreception.

TPC bit decoding circuit 107 extracts TPC bits from the reproductiondata and supplies the decoded instructions for increasing/decreasing thetransmission power that have been transmitted from the mobile station.

TPC bit monitor circuit 108 monitors the changes in prescribed intervalsin the instructions for increasing/decreasing the transmission powerthat have been decoded by TPC bit decoding circuit 107. The TPC bitdecoding results are assumed to repeat in order between instructions fordecreasing and instructions for increasing the transmission power whenthe peak direction of the transmission beam is correctly directed towardthe desired wave mobile station. In other words, within a prescribedtime interval that has been determined in advance, the transmissionpower from a radio base station to a desired wave mobile stationrepeatedly increases and decreases with a particular transmission power(the threshold value power) as center, as shown in FIG. 3A. In thiscase, the number of instructions for increasing and the number ofinstructions for decreasing in the TPC bits are substantially identicalin the prescribed time interval.

On the other hand, if the peak direction of the transmission beamdiverges from the direction of the desired wave mobile station, it isassumed that the desired wave mobile station will continue to requestthe radio base station for an increase in transmission power until thedesired reception quality is obtained, and instructions for increasewill be continuously supplied as output from the decoding results of TPCbits. In other words, the transmission power from the radio base stationto the desired wave mobile station will continuously increase in stepsin the prescribed time intervals as shown in FIG. 3B. In this case, thedesired wave mobile station finally obtains the desired receptionquality, but other mobile stations that are present in the peakdirection of the transmission beam that is formed by the radio basestation directly receive unnecessary interference power, and thereception quality is therefore greatly degraded.

As a countermeasure for this problem, in the present embodiment, thepeak direction of the transmission beam is moved to the right and leftby transmission antenna weight control circuit 109 when the results ofdecoding TPC bits within a prescribed time interval are biased towardinstructions for increasing the transmission power. More specifically,second transmission antenna weights W″=(w″₁, w″₂, . . . , w″_(N)) aregenerated such that the peak direction moves to the right or to the leftwith respect to the transmission beam that is formed by firsttransmission antenna weights W′=(w′₁, w′₂, . . . , w′N). These secondtransmission antenna weights cause the increase or decrease of theamplitude of the transmission data to thus control the peak direction ofthe transmission beam. This process is executed until the bias towardinstructions for increasing the transmission power in the results ofdecoding TPC bits is eliminated, or until the number of movements of thepeak direction reaches a maximum value that has been set in advance.Transmission antenna weight control circuit 109 of the presentembodiment is provided with a register for holding each of the values ofangle L, which is the unit of movement when moving the peak direction tothe right or left, variable K (initial value=0) that indicates thenumber of movements, and Kmax, which is the maximum number of changes(the maximum value of the number of movements).

The configuration and operations of each of receiving-side multipliers102_1-102_N, adder 103, reception antenna weight generation circuit 104,and transmission-side multipliers 106_1-106_N are the same as for theadaptive antenna transceiving device of the prior art that was shown inFIG. 1, and an explanation of the configuration and operations istherefore here omitted.

The following explanation regards the method of controlling thetransmission beam by means of the adaptive antenna transceiving deviceof the present embodiment with reference to FIGS. 4 and 5.

As shown in FIG. 4, in the adaptive antenna transceiving device of thepresent embodiment, the peak direction is moved a predetermined angle Ltoward the right (or left) with respect to the direction (initialposition) of transmission beam 3 that is formed by first transmissionantenna weights W′=(w′₁, w′₂, . . . , w′_(N)) when the results ofdecoding TPC bits in a prescribed time interval are biased towardinstructions for increasing the transmission power (“a” of FIG. 4).Then, if conditions do not improve (the results of decoding TPC bits arebiased toward instructions for increasing transmission power), the peakdirection is further moved by angle L toward the right (or left) (“b” ofFIG. 4). The same process is repeated up to a maximum number of changesKmax that has been set in advance.

If the conditions do not improve despite the maximum number of changesKmax of movements of the peak direction of the transmission beam, thepeak direction is moved by units of angle L in the reverse directiontoward the left (or right) (“c,” “d,” “e,” and “f” of FIG. 4). Here, themaximum number of changes in the reverse direction is 2 Kmax.

By means of the above-described process, the peak direction of thetransmission beam is moved within a maximum range of ±Kmax×L (“+” beingthe right direction and “−”being the left direction) degrees. The valuesof Kmax and L can be changed to any value by instructions from theoutside. FIG. 4 shows an example in which Kmax is set to 2 and in which,after two movements in units of angle L toward the right and fourmovements in units of angle L toward the left, the peak directionreturns to the original initial position (“g” and “h” of FIG. 4).

As shown in FIG. 5, transmission antenna weight control circuit 109 ofthe present embodiment, upon receiving the decoding results from TPC bitmonitor circuit 108, first resets variable K that shows the number ofmovements of the peak direction to “0” (Step S1), and then determines ifthe results of decoding TPC bits that are transmitted from the mobilestation have a bias toward instructions for increasing the transmissionpower (Step S2). If the results of decoding TPC bits are biased towardinstructions for increasing the transmission power, transmission antennaweight control circuit 109 sets the value of second transmission antennaweights W″=(w″₁, w″₂, . . . , w″_(N)) such that the peak direction ofthe transmission beam is moved by L degrees toward the right (or left)(Step S3). Transmission antenna weight control circuit 109 furtherincrements by “1” the value of variable K that shows the number ofmovements of the peak direction (Step S4). If the results of decodingTPC bits have a bias toward instructions for decreasing the transmissionpower, or if there is no bias toward either direction, transmissionantenna weight control circuit 109 supplies first transmission antennaweights that have been generated by antenna weight conversion circuit105 without change as second transmission antenna weights and halts thecontrol process of the transmission beam of the present embodiment.

Transmission antenna weight control circuit 109 next determines whetherthe value of variable K has reached the maximum number of changes Kmax(Step S5), and if the value has not reached the maximum number ofchanges Kmax, returns to the process of Step S2 and repeats theprocesses of Step S2-S5.

When the value of variable K reaches the maximum number of changes Kmax,transmission antenna weight control circuit 109, after resetting thevalue of variable K (Step S6), determines whether the results ofdecoding TPC bits that have been transmitted from the mobile stationhave a bias toward instructions for increasing transmission power (StepS7). If there is a bias toward instructions for increasing transmissionpower in the results of decoding TPC bits, transmission antenna weightcontrol circuit 109 sets the values of second transmission antennaweights W″=(w′₁, w″₂, . . . , w″_(N)) such that the peak direction ofthe transmission beam moves L degrees toward the left (or the right),which is the opposite of the direction up to this point (Step S8).Transmission antenna weight control circuit 109 further increments by“1” the value of variable K, which indicates the number of movements ofthe peak direction (Step S9). If the results of decoding TPC bits show abias toward instructions for decreasing the transmission power, or ifthere is no bias toward either direction, transmission antenna weightcontrol circuit 109 supplies as output the first transmission antennaweights that have been generated by antenna weight conversion circuit105 without alteration as second transmission antenna weights and haltsthe control process of the transmission beam of the present embodiment.

Transmission antenna weight control circuit 109 next determines whetherthe value of variable K has reached the maximum number of changes 2 Kmaxthat has been set in advance (Step S10), and if the value of variable Khas not reached the maximum number of changes 2 Kmax, returns to theprocess of Step S7 and repeats the processes of Step S7-S10. If thevalue of variable K has reached the maximum number of changes 2 Kmax,transmission antenna weight control circuit 109 supplies as output thefirst transmission antenna weights that have been generated by antennaweight conversion circuit 105 without alteration as the secondtransmission antenna weights and halts the control process of thetransmission beam of the present embodiment.

In FIGS. 4 and 5, an example is shown in which the peak direction of thetransmission beam is moved to the right and left by units of angle L,but the angle of movement may be an integer multiple of angle L (otherthan zero) that has been set in advance. For example, when the peakdirection of the transmission beam is at the position +Kmax×L or−Kmax×L, the peak direction may be moved as far as the initial positionin one operation.

According to the adaptive antenna transceiving device of the presentembodiment, if the results of decoding TPC bits in a prescribed timeinterval indicate a bias toward instructions for increasing transmissionpower, the peak direction of the transmission beam can be corrected tothe direction of the desired wave mobile station by shifting the peakdirection of the transmission beam to the right or left. The presentembodiment therefore enables a reduction of the interference power thatis applied to other mobile stations that are present in the peakdirection due to shifting of the peak direction of the transmission beamfrom the mobile station that is the object of transmission, and cantherefore prevent a decrease in the subscriber capacity of the system.

Second Embodiment

In the adaptive antenna transceiving device of the second embodiment,the transmission beam control procedure by transmission antenna weightcontrol circuit 109 differs from that of the first embodiment. Theconfiguration and operations are otherwise the same as the firstembodiment, and redundant explanation is therefore omitted.

As shown in FIG. 6, in the adaptive antenna transceiving device of thesecond embodiment, a process is executed by transmission antenna weightcontrol circuit 109 for alternately moving the peak direction oftransmission beam 3 toward the left and right when the results ofdecoding the TPC bits in a prescribed interval show a bias towardinstructions for increasing the transmission power. In the presentembodiment, the peak direction is moved toward the right (or toward theleft) by angle L that has been set in advance (“a” of FIG. 6) withrespect to transmission beam 3 that is formed by first transmissionantenna weights W′=(w′₁, w′₂, . . . , w′_(N)). If the conditions are notimproved (the results of decoding TPC bits show a bias towardinstructions for increasing the transmission power), the peak directionis moved by angle 2L toward the left (or right) (“b” of FIG. 6). If theconditions are still not improved, the peak direction is moved by angle3L toward the right (or left) (“c” of FIG. 6). The same process isfurther repeated. In this case, the maximum number of changes is assumedto be 2 Kmax that has been set in advance.

Transmission antenna weight control circuit 109 of the presentembodiment is provided with a register for holding each of the valuesof: angle L, which is the unit of movement when moving the peakdirection toward the right and left; variable J (a positive integer,initial value=1) for multiplying angle L; variable K (initial value=0)that shows the number of times of movement; and Kmax that is the maximumnumber of changes (the maximum number of movements).

The above-described process changes the peak direction of thetransmission beam within a maximum range of +Kmax×L (where “+” is towardthe right and “−” is toward the left) degrees. The values of Kmax and Lcan be changed to any value by instructions from the outside. FIG. 6shows an example in which Kmax has been set to 2.

As shown in FIG. 7, upon acquiring the decoding results of TPC bitmonitor circuit 108, transmission antenna weight control circuit 109 ofthe second embodiment first resets the value of variable K, which showsthe number of times the peak direction has been moved, to “0,” and thensets the value of variable J for multiplying angle L to “1” (Step S11).

Transmission antenna weight control circuit 109 next determines whetherthe results of decoding the TPC bits that are transmitted from themobile station are biased toward instructions for increasing thetransmission power (Step S12), and if the results of decoding the TPCbits are biased toward instructions for increasing the transmissionpower, transmission antenna weight control circuit 109 sets the valuesof second transmission antenna weights W″=(w″₁, w″₂, . . . , w″_(N))such that the peak direction of the transmission beam moves +J×L (or−J×L) (Step S13). Transmission antenna weight control circuit 109 nextincrements by “1” each of the values of variable K that shows the numberof movements of the peak direction and variable J for multiplying angleL, and further multiplies angle L by −1 (Step S14). If the results ofdecoding TPC bits are biased toward instructions for decreasing thetransmission power, or if the results are not biased toward eitherincrease or decrease, transmission antenna weight control circuit 109supplies as output the first transmission antenna weights that have beengenerated by antenna weight conversion circuit 105 without alteration assecond transmission antenna weights and halts the control process of thetransmission beam of the present embodiment.

Transmission antenna weight control circuit 109 next determines whetherthe value of variable K has reached the maximum number of changes 2 Kmaxthat has been set in advance (Step S15), and if the value of variable Khas not reached the maximum number of changes 2 Kmax, transmissionantenna weight control circuit 109 returns to the process of Step S12and repeats the processes of Step S12-S15. However, if the value ofvariable K has reached the maximum number of changes 2 Kmax,transmission antenna weight control circuit 109 supplies as output thefirst transmission antenna weights that have been generated by antennaweight conversion circuit 105 without alteration as the secondtransmission antenna weights and halts the control process of thetransmission beam of the present embodiment.

As in the first embodiment, the adaptive antenna transceiving device ofthe second embodiment can correct the peak direction of the transmissionbeam to the direction of the desired wave mobile station and thus canreduce the interference power that is applied to other mobile stationsthat are present in the peak direction that is caused when the peakdirection of the transmission beam diverges from the mobile station thatis the object of transmission. Accordingly, the adaptive antennatransceiving device of the second embodiment can prevent the reductionof the subscriber capacity of a system.

Third Embodiment

In the adaptive antenna transceiving device of the third embodiment, thecontrol procedure of the transmission beam by means of the transmissionantenna weight control circuit differs from that of the first embodimentand the second embodiment. The configuration and operations areotherwise identical to the first embodiment, and redundant explanationis therefore omitted.

In the adaptive antenna transceiving device of the third embodiment,when the results of decoding the TPC bits are biased toward instructionsfor increasing the transmission power, the width of the main lobe isincreased by a preset angle of ±H (where “+” is toward the right and “−”is toward the left) with respect to the transmission beam that is formedby the first transmission antenna weights W′=(w′₁, w′₂, . . . , w′_(N)).If the conditions do not then improve (if the results of decoding theTPC bits are still biased toward instructions for increasingtransmission power), the width of the main lobe of the transmission beamis again increased by an angle of ±H. The same process is subsequentlyrepeated. In this case, the maximum number of changes is preset as Kmax.

The width of the main lobe of the transmission beam is changed by theabove-described process within a maximum range of Kmax×2H degrees. Whenthe width of the main lobe of the transmission beam is increased in thisway, the reception power in the mobile station that is the object oftransmission increases even if the peak direction of the transmissionbeam should diverge slightly from the mobile station, thus limitingincrease in the transmission power that results from divergence of thepeak direction of the transmission beam from the mobile station that isthe object of transmission. In addition, because excessive increase ofthe width of the main lobe in the present embodiment appliesinterference power to other mobile stations that are present in thevicinity of the desired wave mobile station, angle H and maximum numberof changes Kmax are preferably set to minimum values.

Transmission antenna weight control circuit 109 of the presentembodiment is provided with a register for holding the values of eachof: angle H, which is the unit of change of the main lobe width;variable K that shows the number of changes of the main lobe width; andthe maximum number of changes Kmax. The values of Kmax and H can bechanged to any value in accordance with instructions from the outside.

As shown in FIG. 8, upon acquiring decoding results from TPC bit monitorcircuit 108, transmission antenna weight control circuit 109 of thepresent embodiment first resets the value of variable K that shows thenumber of changes of the main lobe width to “0” (Step S21), and thendetermines whether the results of decoding the TPC bits that have beensent from the mobile station are biased toward instructions forincreasing the transmission power (Step S22). If the results of decodingTPC bits are biased toward instructions for increasing the transmissionpower, transmission antenna weight control circuit 109 sets the value ofsecond transmission antenna weights W″=(w″₁, w″₂, . . . , w″_(N)) suchthat the width of the main lobe of the transmission beam is increased by+H degrees (Step S23). Transmission antenna weight control circuit 109further increments by “1” the value of variable K that shows the numberof changes of the main lobe width (Step S24). If the results of decodingthe TPC bits are biased toward instructions for decreasing thetransmission power, or if there is no bias toward either increasing ordecreasing the transmission power, transmission antenna weight controlcircuit 109 supplies as output the first transmission antenna weightsthat have been generated by antenna weight conversion circuit 105without alteration as the second transmission antenna weights and haltsthe control process of the transmission beam of the present embodiment.

Transmission antenna weight control circuit 109 next determines whetherthe value of variable K has reached the maximum number of changes Kmaxthat has been set in advance (Step S25), and if the value of variable Khas not reached the maximum number of changes Kmax, returns to Step S22and repeats the processes of Step S22-S25. On the other hand, if thevalue of variable K has reached the maximum number of changes Kmax,transmission antenna weight control circuit 109 supplies as output thefirst transmission antenna weights that have been generated by antennaweight conversion circuit 105 without alteration as the secondtransmission antenna weights and halts the control process of thetransmission of the present embodiment.

The adaptive antenna transceiving device of the third embodiment limitsincrease in the transmission power that results when the peak directionof the transmission beam diverges from the mobile station that is theobject of transmission and is therefore able to reduce the interferencepower that is applied to other mobile stations that are present in thepeak direction of the transmission beam and prevent decrease of thesubscriber capacity of the system.

Fourth Embodiment

In the first to third embodiments, examples were shown in which the peakdirection of the transmission beam was controlled by increasing ordecreasing the amplitude of transmission data by means of secondtransmission antenna weights.

However, an adaptive antenna transceiving device can also use theabove-described radio signal transceiver to control transmission power.Radio signal transceivers 210_1-210_N are provided with, as RFtransmitters, an orthogonal modulator for orthogonally modulatingbaseband signals, an up-converter for converting baseband signals toradio frequencies, AGC (Automatic Gain Control), and TPA (TransmissionPower Amplifier) (these components not being shown in the figure); and,as shown in FIG. 9, radio signal transceivers 210_1-210_N are arrangedbetween antenna devices and transmission-side multipliers.

In the present embodiment, the monitor results of the TPC bit monitorcircuit are supplied to radio signal transceivers 210_1-210_N, and aswith the transmission antenna weight control circuit that was shown inthe first to third embodiments, the power that is supplied to each ofthe antenna devices is controlled by, for example, the AGC that isprovided in radio signal transceivers 210_1-210_N. This configurationcan obtain the same effect as the first to third embodiments.

Fifth Embodiment

FIG. 10 is a block diagram showing an example of the configuration of aradio base station that is provided with the adaptive antennatransceiving device of the present invention.

As shown in FIG. 10, radio base station 1 of the present embodiment is aconstruction that includes: adaptive antenna transceiving device 11 thatwas shown in the first to fourth embodiments; control unit 12 forcontrolling the operations as a radio base station, such as themultiplexing and separation of the transceiving data for each mobilestation and the monitoring of the communication states with each mobilestation; and communication interface device 13, which is the interfacewith radio network control device 2 for both controlling the position ofeach mobile station and relaying communication between mobile stationsand a network by way of a plurality of radio base stations 1.

As in the present embodiment, the use of adaptive antenna transceivingdevice 11 that was shown in the first to fourth embodiments in radiobase station 1 realizes a radio base station that prevents decrease inthe subscriber capacity of a mobile communication system.

1. A transmission beam control method for controlling the transmissionbeam of an adaptive antenna transceiving device that is provided with aplurality of antenna devices; said method comprising: a first step forextracting, from received signals that have been received by saidplurality of antenna devices, TPC bits that are used for controllingtransmission power, and decoding from said TPC bits increase/decreaseinstructions indicating instructions for increasing or instructions fordecreasing said transmission power; a second step for monitoring changesin said increase/decrease instructions in prescribed time intervals thathave been set in advance and determining whether or not saidincrease/decrease instructions are biased toward instructions forincreasing said transmission power; a third step for, when saidincrease/decrease instructions are biased toward instructions forincreasing said transmission power, changing a directivity of saidtransmission beam from a prescribed directivity that is formed based onthe directivity during reception; and a fourth step for repeating saidfirst step to third step until the bias of said increase/decreaseinstructions toward instructions for increasing said transmission poweris eliminated or until the number of times of changing said transmissionbeam reaches a maximum value that has been set in advance.
 2. Thetransmission beam control method according to claim 1, wherein, whensaid increase/decrease instructions are biased toward said instructionsfor increasing said transmission power, the peak direction of saidtransmission beam is moved from the same directivity as during receptionin angle units that have been set in advance.
 3. The transmission beamcontrol method according to claim 2, wherein the peak direction of saidtransmission beam is moved by integer multiples, other than zero, of anangle that has been set in advance.
 4. The transmission beam controlmethod according to claim 1, wherein, when said increase/decreaseinstructions are biased toward instructions for increasing saidtransmission power, the width of the main lobe of said transmission beamis increased by angle units that have been set in advance.
 5. Anadaptive antenna transceiving device for controlling transmission powerand directivity of a transmission beam that uses a plurality of antennadevices; said adaptive antenna transceiving device comprising: a TPC bitdecoding circuit for extracting, from received signals that have beenreceived by said plurality of antenna devices, TPC bits that are usedfor controlling transmission power, and decoding from said TPC bitsincrease/decrease instructions indicating instructions for increasing orinstructions for decreasing said transmission power; a TPC bit monitorcircuit for monitoring changes in prescribed time intervals of saidincrease/decrease instructions that have been decoded by said TPC bitdecoding circuit, and determining whether or not said increase/decreaseinstructions are biased toward instructions for increasing saidtransmission power; and a transmission antenna weight control circuitfor, when said increase/decrease instructions are biased towardinstructions for increasing said transmission power, generatingtransmission antenna weights that correspond to amplitudes that aresupplied to each of said antenna devices such that a directivity of saidtransmission beam changes from a prescribed directivity that is formedbased on the directivity during reception; and repeating the processesfor changing the directivity of the transmission beam until the bias ofsaid increase/decrease instructions toward instructions for increasingsaid transmission power is eliminated, or until the number of changes ofsaid transmission beam reaches a maximum value that has been set inadvance.
 6. The adaptive antenna transceiving device according to claim5, wherein said transmission antenna weight control circuit, when saidincrease/decrease instructions are biased toward instructions forincreasing said transmission power, controls said transmission antennaweights such that the peak direction of said transmission beam movesfrom the same directivity as during reception in angle units that havebeen set in advance.
 7. The adaptive antenna transceiving deviceaccording to claim 6, wherein said transmission antenna weight controlcircuit controls said transmission antenna weights such that the peakdirection of said transmission beam moves in multiples, other than zero,of an angle that has been set in advance.
 8. The adaptive antennatransceiving device according to claim 5, wherein said transmissionantenna weight control circuit, when said increase/decrease instructionsare biased toward instructions for increasing said transmission power,controls said transmission antenna weights such that the width of themain lobe of said transmission beam increases in prescribed angle unitsfrom a value that has been set in advance.
 9. An adaptive antennatransceiving device for controlling the transmission beam andtransmission power using a plurality of antenna devices; said adaptiveantenna transceiving device comprising: a TPC bit decoding circuit forextracting, from received signals that have been received by saidplurality of antenna devices, TPC bits that are used for controllingtransmission power; and decoding from said TPC bits increase/decreaseinstructions indicating instructions for increasing or instructions fordecreasing said transmission power; a TPC bit monitor circuit formonitoring changes in prescribed time intervals in saidincrease/decrease instructions that have been decoded at said TPC bitdecoding circuit and determining whether or not said increase/decreaseinstructions are biased toward instructions for increasing saidtransmission power; and a radio signal transceiver for, when saidincrease/decrease instructions are biased toward instructions forincreasing said transmission power, controlling the power that issupplied to each of said antenna devices such that a directivity of saidtransmission beam changes from a prescribed directivity that is formedbased on the directivity during reception, and for repeating theprocesses for changing the directivity of said transmission beam untilthe bias of said increase/decrease instructions toward instructions forincreasing said transmission power is eliminated or until the number ofchanges of said transmission beam reaches a maximum value that has beenset in advance.
 10. The adaptive antenna transceiving device accordingto claim 9, wherein said radio signal transceiver, when saidincrease/decrease instructions are biased toward instructions forincreasing said transmission power, controls the power that is suppliedto each of said antenna devices such that the peak direction of saidtransmission beam is moved by an angle unit that has been set in advancefrom the same directivity as during reception.
 11. The adaptive antennatransceiving device according to claim 10, wherein said radio signaltransceiver controls the power that is supplied to each of said antennadevices such that the peak direction of said transmission beam moves byinteger multiples, other than zero, of an angle unit that has been setin advance.
 12. The adaptive antenna transceiving device according toclaim 9, wherein said radio signal transceiver controls power that issupplied to each of said antenna devices such that, when saidincrease/decrease instructions are biased toward instructions forincreasing said transmission power, the width of the main lobe of saidtransmission beam is increased by prescribed angle units from a valuethat has been set in advance.
 13. A radio base station, comprising: anadaptive antenna transceiving device according to claim 5; a controlunit for monitoring communication states with each mobile station andthe multiplexing/separation of transmission/reception data of eachmobile station; and a communication interface device, which is theinterface with a radio network control device for relaying communicationbetween said mobile stations and a network.
 14. A radio base station,comprising: an adaptive antenna transceiving device according to claim9; a control unit for monitoring communication states with each mobilestation and the multiplexing/separation of transmission/reception dataof each mobile station; and a communication interface device, which isthe interface with a radio network control device for relayingcommunication between said mobile stations and a network.